Furnace combustion tube and mounting assembly

ABSTRACT

A combustion tube mounting system releasably mounts a combustion tube to an aperture in the floor of a furnace housing. The combustion tube has a base assembly with a cam and can be manually or automatically unlocked by cam pins in the floor for selectively engaging the cam for lowering the combustion tube from the floor of the furnace. When a new combustion tube is placed on the lower seal assembly and raised, it automatically aligns and engages the upper furnace seal and engages cams on the floor of the furnace housing which lock the combustion tube in place as it is introduced into the furnace.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/889,628, filed Sep. 24, 2010, entitled EASILY REMOVABLE COMBUSTIONTUBE, which claimed priority under 35 U.S.C. §119(e), and the benefit ofU.S. Provisional Application No. 61/245,732 entitled EASY REMOVABLECOMBUSTION TUBE, filed on Sep. 25, 2009, by Gordon C. Ford, et al., theentire disclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a combustion furnace for an analyzerand particularly to the removable mounting of a combustion tube therein.

The combustion of inorganic solid samples using an induction furnacerequires a pressurized oxygen-rich environment. A quartz combustion tubeis typically used to maintain this pressurized environment but becomescoated with byproducts of combustion during the combustion process. Thequartz tube must be cleaned and eventually replaced to maintain theaccuracy of sample results. The mounting of a combustion tube inexisting furnaces equipped with an auto cleaner is both time consumingand cumbersome, requiring that fluid fittings and electrical connectionsbe removed and the auto-cleaner device removed from the combustion tubearea of the furnace. The combustion tube is removed from the front ofthe furnace housing once the disassembly has been completed. Once a newcombustion tube has been installed, the furnace has to be reassembled,frequently including the connection of fluid couplings which can lead toleaks in the system if not properly accomplished. Thus, the maintenance,removal and replacement of combustion tubes in existing furnaces isdifficult, time consuming, and leads to downtime for the operation of ananalyzer.

Accordingly, there exists a need for an improved analytical combustionfurnace in which a combustion tube can be readily accessed withoutdisconnecting fluid fittings, auto-cleaners, or the like from thefurnace assembly.

SUMMARY OF THE INVENTION

The system of the present invention accomplishes this goal by providinga combustion tube mounting system in which the combustion tube isremovably installed through an aperture in the floor of the furnacehousing. The combustion tube can be manually or automatically unlockedfrom the floor of the furnace housing by a cam-locking mechanism forpositioning the combustion tube in an open area of the furnace below thefurnace housing for easy removal and replacement.

In a preferred embodiment, a combustion tube includes a base sealassembly which is placed on the lower seal assembly and raised toautomatically align with the upper furnace seal. Cams in the floor ofthe furnace housing engage a cam associated with the base seal assemblyto lock the combustion tube in place as it is raised into the furnacehousing. As a result of this downwardly removable combustion tube, thesteps of disassembling the furnace components, including theself-cleaning mechanism located above the combustion tube, is eliminatedas is the necessity for skilled technicians to replace the combustiontube. An operator can easily unlock the combustion tube from the furnaceand lower it for access and replacement.

These and other features, objects and advantages of the presentinvention will become apparent upon reading the following descriptionthereof together with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front perspective view of a furnace embodying the presentinvention;

FIG. 2 is an enlarged front perspective view of the furnace housing withthe cover removed showing the combustion tube locking mechanism in anunlocked position;

FIG. 3 is a perspective view of the combustion tube with its base sealassembly;

FIG. 4 is an exploded perspective view of the base seal assembly;

FIG. 5 is a cross-sectional view of the assembled base seal assembly;

FIG. 6 is a front perspective view of the furnace shown with the lockingmechanism in an unlocked position;

FIG. 7 is a partial front perspective view of the furnace shown in FIG.6, shown with the cover removed;

FIG. 8 is a front perspective view of the furnace shown in FIG. 7,showing the lowering and raising of the combustion tube through anaperture in the furnace housing floor;

FIG. 9 is a front perspective view of the furnace shown in FIG. 8,showing the combustion tube lowered from the furnace housing in aposition for removal/replacement;

FIG. 10 is a bottom perspective view of the furnace housing;

FIG. 11 is a left front exploded perspective view of the furnace housingand locking mechanism for the combustion tube;

FIG. 12 is a right front perspective view of the assembled furnacehousing;

FIG. 13 is a fragmentary vertical cross-sectional view of the camlocking mechanism for the combustion tube;

FIG. 14 is a fragmentary vertical cross-sectional view of a combustiontube shown in a locked position within the floor of the furnace housing;and

FIG. 15 is a fragmentary vertical cross-sectional view showing thecombustion tube in an unlocked position for removal.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring initially to FIG. 1, there is shown an analyzer 10 whichincludes an induction furnace assembly 20, including the auto cleaningmechanism 30 described in detail in U.S. Provisional Patent ApplicationSer. No. 61/373,014, filed Aug. 12, 2010, entitled COMBUSTION FURNACEAUTO CLEANER, the disclosure of which is incorporated herein byreference. The analyzer components themselves can be similar to thoseemployed in a carbon sulfur analyzer, Model No. CS600, available fromLeco Corporation of St. Joseph, Mich. The analyzer 10 is shown in FIG. 1with the cover shrouds removed to expose the components of the inductionfurnace, which are also shown in FIGS. 2-5. The detachable auto cleanerassembly 30 is removably mounted by a bayonet connection to a heatedfilter assembly 40, which is sealably secured at 65 to the top wall 51of combustion housing 50. Housing 50 additionally includes side walls 53and 55, an interface back wall 57, and floor 58, as best seen in FIGS.7-12. The housing 50 is mounted to structural base 17 of the analyzer10, which includes housing 50. The front of furnace housing 50 isenclosed by a quickly removable door 52, which, when removed as seen inFIG. 2, exposes an induction coil 61 which surrounds a combustion tube60 (FIG. 7) in a conventional manner to heat an analytical specimen heldin a ceramic crucible 14 (FIG. 1) when introduced into the hot zone ofcombustion tube 60 by vertically movable pedestal 12. Tube 60 issealably coupled to the lower end of filter assembly 40 by an upper sealassembly 65 in a conventional manner. The pedestal 12 (FIG. 1) forholding a sample-holding crucible 14 is positioned on a cup-shaped lowerseal assembly 16 and is raised and lowered into combustion tube 60 bymeans of a pneumatic cylinder 18 and cylinder rod 22 (FIG. 7) coupled toassembly 16. In the position shown in FIG. 1, the cylinder rod 22 is ina lowered retracted position within cylinder 18.

A combustion tube base assembly 80 (FIGS. 3-5) sealably couples thelower end of tube 60 to lower seal assembly 16 such that, duringcombustion of a sample, oxygen flows upwardly through a gas inlet inassembly 16 to sweep byproducts of combustion into gas outlet 13(FIG. 1) for analysis. Oxygen is also supplied to the upper end ofcombustion tube 60 by an oxygen inlet 15 and suitable passageways to aninlet lance to direct oxygen into crucible 14 during combustion. Housing50 includes cam-actuated locking assembly 100 which cooperates with baseassembly 80 to allow the combustion tube 60 to be easily withdrawn fromunderneath the floor of combustion housing 50, as described later.

Combustion tube 60 can be a conventional quartz combustion tubeavailable from Leco Corporation, Part No. 619-590-775 or its equivalent.The combustion tube, as seen in FIGS. 3-5, includes a base assembly 80having a generally cylindrical collar 82 with a central aperture 81therein for receiving the combustion tube 60, as seen in FIG. 3. Nearthe upper edge of collar 82 is an annular recess 83 for receiving anO-ring seal 84. A locking cap 85 is threaded onto collar 82 andcompresses the O-ring seal once the combustion tube has been insertedtherein for sealably holding the combustion tube within the collar 82.Collar 82 includes a lower cylindrical sleeve 86 having internal annularrecess 87 for receiving a second O-ring 88 for sealing the base assembly80 onto the lower seal assembly 16. Further, the assembly 80 includes ametal RFI shield 89 and a third sealing O-ring 78 (FIGS. 14 and 15)positioned within an annular recess 91 of collar 82.

Collar 82 includes a cam 90 which has an outer annular vertical surface92, an upper chamfered surface 94 chamfered upwardly and inwardly at anangle of about 45° from the vertically extending annular surface 92 anda lowered chamfered surface 96 inwardly and downwardly beveled at anangle of about 45° from surface 92. The two surfaces thus form an angleof about 90° between them to fit (as described below with respect toFIG. 14) within a 90° slot 107. Collar 82 also includes an annularflange 93 having a diameter greater than aperture 59 in furnace housingfloor 58 to engage the undersurface of floor 58 when the combustion tubeis in an installed locked position as seen in FIG. 14. The cam 90so-defined interengages with the cam pins 106 and 108 of cam-actuatedassembly 100 for locking and unlocking the combined combustion tube 60and base assembly 80 (shown in FIG. 3) as now described.

FIGS. 7-15 illustrate the removal of the combustion tube 60 from thefurnace housing 50 and, for purposes of clarity, the induction coils andother parts unnecessary to the description of the cam-actuatedcombustion tube mounting arrangement have been deleted from thesefigures. Also, in FIGS. 7-10, the pneumatic actuators for automaticallyoperating the cam-actuated assembly 100 are not shown as these figuresare primarily for the purpose of illustrating the motion of thecombustion tube during its removal and replacement. FIGS. 7-9 illustratethe motion of the combustion tube when cylinder 18 is moved to aretracted position once the cam-actuated assembly 100 has been moved toan unlocked position allowing, as seen in FIG. 8, the combustion tube tobe lowered through the circular aperture 59 (FIG. 10) in the floor 58 offurnace housing 50. When lowered to a position as seen in FIG. 9, thecombustion tube 60 and base assembly 80 can be lifted from the lowerseal assembly 16 and combustion tube 60 replaced with a new combustiontube by loosening locking ring 85, allowing the tube to be removed fromthe base assembly 80. The cam-actuated assembly 100 cooperates with thecam 90 of the combustion tube base assembly 80 to form a releasablelocking mechanism to lockably hold and alternately release thecombustion tube 60 from below the furnace housing 50.

Assembly 100 is used for either manually or automatically unlocking thecombustion tube 60 (and attached base assembly 80) from the combustionhousing 50 as best seen in FIGS. 11-15. Floor 58 of combustion housing50 includes a pair of blind cylindrical apertures 102 and 104, whichrotatably receive cam pins 106 and 108 of mechanism 100. Apertures 102and 104 are formed and sized to intersect opposite edges of aperture 59in floor 58 and are positioned such that generally V-shaped 90° slots107 on the inner-facing edges of pins 106 and 108 are exposed throughopenings 111 in the so truncated cylindrical side wall of aperture 59.Springs 110 and 112 engage the inner ends of pins 106 and 108, which areretained within the apertures 102 and 104 by a mounting plate 114secured to the front face 116 of floor 58 by fasteners 118 extendingthrough apertures 120 in mounting plate 114. A pair of manually actuatedhandles 122 and 124 are pinned to apertures 123 and 125, respectively,near the ends of cam pins 106, 108, such that pins 106 and 108 can bemanually rotated by the manipulation of the operator of handles 122 and124 rotating them inwardly, as seen, for example, in FIGS. 7-10, to anunlocking position. Springs 110, 112 urge handles 122, 124 into concaverecesses 113, 115 on the inner facing surface of plate 114 urging theminto a releasable locked position (FIGS. 1 and 12-14). In the unlockedposition illustrated in FIG. 15, the handles are rotated out of recesses113, 115 rotating the 90° slots 107 of pins 106 and 108 to a position inwhich surfaces 105 and 109 of slots 107, which normally engage thechamfers 94 and 96 on cam 90 of assembly 80, respectively, release cam90 allowing, as seen in FIG. 15, the combustion tube 60 and baseassembly 80 to be lowered downwardly in the direction indicated by arrowA for removal when in the position shown in FIG. 9. Surfaces 105 andtheir tip junction with cylindrical pins 106 and 108 also urge againstchamfer 94 of cam 90 to assist in freeing base assembly 80 andcombustion tube 60 downwardly from floor 50.

The cam-actuated combustion tube releasing assembly 100 can either bemanually actuated by an operator squeezing the handles 122, 124 towardone another to rotate pins 106, 108 and release the combustion tube 60or the operation can be automated. For such purpose, floor 58 includes apair of arcuate recesses 130 and 132 forwardly of aperture 59 in floor58 and which communicate with apertures 102 and 104 to expose apertures127 and 129 (FIG. 11) on pins 106 and 108, which receive actuator pins131 and 133. Pins 131, 133 extend upwardly from floor 58 and can beengaged, as best seen in FIGS. 12 and 13, by actuator rods 140 and 142of pneumatic cylinders 141 and 143, respectively. Cylinders 141 and 143are secured within recesses 150 in the side walls 53 and 55 of thehousing 50 by fasteners 145 in a conventional manner. Thus, thecam-actuated assembly 100 can either be manually entered by the operatorengaging handles 122 or 124 or electrically by the actuation ofcylinders 141 and 143 to rotate the pins 106 and 108 from a lockingposition, shown in FIG. 14, to an unlocked position, shown in FIG. 15.When in the unlocked position, the combustion tube and its seal assemblycan be dropped downwardly utilizing cylinder 18 to lower the combustiontube 60 into the position shown in FIG. 9 where it can be removed fromthe furnace housing and replaced.

Once the combustion tube has been replaced with a new tube and mountedto the base assembly 80, the cylinder 18 can then be actuated, reversingthe process by raising the combustion tube in an upwardly direction, asseen in FIG. 8, to a locked position shown in FIG. 1. As the combustiontube is raised through aperture 59, the surface 94 of cam 90 engages thecamming surface 105 on pins 106 and 108 rotating them when combustiontube 60 is moved in the direction opposite arrow A in FIG. 15, to againmove the locking pins 106, 108 to the locked position illustrated inFIG. 14. In this position, surfaces 105, 109 on pins 106, 108 engage thechamfered surfaces 94, 96, respectively, of cam 90 and securely hold thecombustion tube 60 in place with the flange 93 of the base assemblyengaging the lower surface of floor 58 of the furnace housing 50. Asseen in FIG. 15, the pins 106 and 108 extend sufficiently outwardlythrough slots 111 in the cylindrical side wall of aperture 59 so as toengage cam 90.

It will become apparent to those skilled in the art that variousmodifications to the preferred embodiment of the invention as describedherein can be made without departing from the spirit or scope of theinvention as defined by the appended claims.

The invention claimed is:
 1. A combustion furnace for an analyzercomprising: a furnace housing having a floor with an aperture thereinfor receiving a combustion tube; a generally cylindrical combustiontube; and a lower seal assembly coupled to said combustion tube andmovable between a raised position and a lowered position for raisingsaid combustion tube into said housing and lowering said combustion tubefrom said housing through said aperture in said floor.
 2. The furnace asdefined in claim 1 wherein said combustion tube includes a base assemblyat a lower end and wherein said floor of said housing includes a lockingassembly which selectively engages said base assembly for holding saidcombustion tube in a use position within said furnace housing.
 3. Thefurnace as defined in claim 2 wherein said locking assembly includes atleast one rotatable cam which engages said base assembly when saidcombustion tube is raised within said aperture by said lower sealassembly.
 4. The furnace as defined in claim 3 wherein said baseassembly includes a cam which cooperates with said rotatable cam of saidlocking assembly to selectively lock and release said combustion tubefrom said floor of said furnace housing.
 5. A combustion furnace for ananalyzer comprising: a generally cylindrical combustion tube; and alower seal assembly removably coupled to a base assembly secured nearone end of said combustion tube said lower seal assembly selectivelyraising and lowering said combustion tube through an aperture in a floorof a combustion furnace.
 6. The furnace as defined in claim 5 whereinsaid base assembly allows said combustion tube to be removed therefrom,said base assembly comprising a collar including a cam, a locking capsurrounding said combustion tube and threadably coupled to said uppercollar and a first annular seal positioned between said upper ring andcollar.
 7. The furnace as defined in claim 6 wherein said cam of saidcollar has an annular outer surface and upper and lower chamferedsurfaces spanning opposite sides of said annular surface.
 8. The furnaceas defined in claim 7 wherein said collar has an internal annular recessspaced from said locking cap and includes a second annular sealpositioned in said recess.
 9. The furnace as defined in claim 8 whereinsaid collar includes a cylindrical sleeve extending in spacedrelationship to said lower chamfered surface, wherein said sleeveincludes an annular recess receiving a third annular seal, said sleeveshaped to sealably extend over a furnace lower seal assembly.
 10. Acombustion furnace for an analyzer comprising: a furnace housing havinga floor with an aperture therein for receiving a combustion tube; agenerally cylindrical combustion tube; a lower seal assembly coupled tosaid combustion tube and movable between a raised position and a loweredposition for raising said combustion tube into said housing and loweringsaid combustion tube from said housing through said aperture in saidfloor; and a releasable locking mechanism extending between saidcombustion tube and said floor for alternately holding said combustiontube in a use position and releasing said combustion tube for removaldownwardly through said aperture.
 11. The furnace as defined in claim 10wherein said releasable locking mechanism includes a cam secured nearone end of said combustion tube for releasably holding said tube saidcombustion furnace housing, and at least one cam pin rotatably mountedto said combustion furnace housing adjacent said aperture for releasablyengaging said cam of said combustion tube.
 12. The furnace as defined inclaim 11 wherein said locking mechanism includes at least a pair of campins on opposite sides of said aperture.
 13. The furnace as defined inclaim 12 wherein said cam includes a pair of spaced-apart beveledsurfaces extending at about 90° with respect to each other.
 14. Thefurnace as defined in claim 13 wherein said cam pins include taperedslots with side walls angled at about 90°, which side walls engage saidbeveled surfaces of said cam to hold said combustion tube in place. 15.The furnace as defined in claim 14 wherein said cam pins include handlesfor rotating said cam pins between a cam engaging position and a camdisengaging position.
 16. The furnace as defined in claim 15 whereinsaid locking mechanism further includes actuators for rotating said campins.